It is known that a polysaccharide having anti-tumor activity can be obtained from a broth which has undergone culture of a fungus of the class Basidiomycetes with an aqueous liquid medium. It is also an established fact that when a fungus of the class Basidiomycetes is subjected to submerged culture with a liquid medium, the desired polysaccharide is produced not only in the mycelia but also in the medium.
Therefore, for producing a polysaccharide from such submerged culture of a fungus of the class Basidiomycetes, there has been generally employed a method in which the mycelia are crushed while keeping the used medium (cultured broth) in the form as it is or after adding water thereto, then the cultured broth is subjected to filtration or centrifugal separation to remove the mycelial residue therefrom, and the desired polysaccharide is collected from the resulting liquor portion.
Although such method is certainly appraised as rational and practical, it still involves some serious problems. For instance, where the submerged culture product is immediately separated into the mycelia and the liquor, such separation can not be accomplished efficiently due to the elevated viscosity of the system and also due to the high water content of the mycelia. Addition of water may decrease the viscosity of the cultured broth and increase the rate of extraction into water, but the use of an excessive amount of water results in an increased time for the separation and does not decrease the water content of the mycelia.
For these reasons, improvements in the method of obtaining a desired polysaccharide from the above-mentioned submerged culture at higher efficiency and in a higher yield from the industrial viewpoint have been demanded.